The present device relates to medical devices, and specifically to improvements to devices such as sphincterotomes, also known as papillotomes.
In endoscopic, or other minimally invasive surgery, generically referred to herein as endoscopic surgery, a sphincterotome may be used in conjunction with an endoscope to provide surgical cutting inside a patient. Specifically, a sphincterotome is used during certain procedures to make an incision in a sphincter. For example, a common treatment of cholecystitis includes the removal of gallstones from the common bile duct. This is frequently done endoscopically with the use of a duodenoscope. The common bile duct proceeds from the junction of the common hepatic duct with the cystic duct, which is open to the gall bladder, and merges with the pancreatic duct, forming the ampulla of Vater, which itself opens into the duodenum at the papilla of Vater. The sphincter of Oddi is a muscular ring that controls passage of fluid from the ampulla of Vater into the duodenum. For removal of gallstones in an endoscopic procedure, access to the common bile duct for removal of gallstones is eased using a sphincterotome to incise or sever the sphincter of Oddi. The sphincterotome is introduced through the duodenoscope and guided through the duodenum to the common bile duct. Once the sphincterotome is guided into the sphincter, its cutting element, commonly a needle knife or cutting wire, is used to incise the sphincter, and thereby improve access to the bile duct and impacted gallstones.
Another example of a common procedure utilizing a sphincterotome is endoscopic retrograde cholangiopancreatography (ERCP), a diagnostic visualization technique used for variety of clinical applications. In this procedure, a contrast fluid such as a radio-opaque dye is introduced through a tube into the ampulla of Vater. A sphincterotome is often employed to provide access through the sphincter of Oddi in the same manner as described above. ERCP is often used in diagnosis of cholecystitis, as well as in the diagnosis and treatment of other conditions of the pancreatic and common bile ducts and related structures.
As illustrated in FIG. 1, a typical prior art sphincterotome 100 includes a polymer tubular shaft 102 made of PTFE (polytetrafluoroethylene) or another flexible material. An electroconductive filament 104, also called a drive wire, is disposed in a lumen 106 running through the shaft 102. The distal end of the filament 104 is connected or anchored to the distal end of the shaft 102. A short segment of the electroconductive filament 104 near the distal end thereof is disposed outside of the shaft 102 for use as an electrocautery cutting wire 108. The proximal end of filament 104 is connected to the proximal handle assembly 110 such that actuation of the handle assembly 110 partially retracts (i.e., pulls in a proximal direction) the filament 104 relative to the polymer shaft 102. This actuation results in the distal end of shaft 102 bowing to form an arc 112, with the exposed filament forming a secant of the arc 112 so as to form a cutting wire 108. Electric current passed through the filament 104 from an electrode 114 in the handle assembly 110 enables the cutting wire 108 to act as an electrosurgical cutting element that may be used effectively to cut and cauterize tissue, such as the sphincter of Oddi in the example procedures described above.
One problem that often arises during or as the result of manufacture of this type of sphincterotome 100 is over-tensioning or under-tensioning of the electroconductive filament 104 relative to the shaft 102 due to length changes of the shaft 102 or filament 104 that may occur after the 104 filament is assembled to the sphincterotome 100. For example, the polymer tube 102 may shrink or elongate as a result of curing or some other post-assembly process (e.g., heating and/or sterilization). However, the electroconductive filament 104 will rarely undergo an identical shrinkage or elongation due to its different composition. As a result, and because the filament 104 and the shaft 102 are fixedly connected at the proximal and distal ends, any change in relative length between the filament 104 and the shaft 102 will generate compressive or tensile forces in these structures. The compressive or tensile forces in the filament 104 and the shaft 102 may interfere with the function of the sphincterotome. For example, if the shaft 102 elongates relative to the filament 104, then the shaft 102 will undergo compression, and the filament 104 will undergo tension (i.e., over-tensioning) which results in bowing of the shaft 102 prior to actuation in surgical use. On the other hand, if the shaft 102 shrinks in length relative to the filament 104, the resulting decrease of relative tension in the filament 104 (i.e., under-tensioning or bagginess) may cause a slackness in the filament 104 that can interfere with the proper actuation of the sphincterotome 100 during surgical use. The present invention provides a mechanism for adjusting the tension in the sphincterotome filament and/or compression in the shaft to alleviate both problems of over-tensioning and under-tensioning.